Recently, organic photoconductors photoconductor (OPC) have been widely used in photocopiers, facsimiles, laser printers, and compound machines thereof instead of inorganic photoconductors, because the organic photoconductors have excellent properties, and various advantages. Examples of the reasons of the favorable use of the organic photoconductors include (1) optical properties such as a wide wavelength range of light absorption, (2) electric properties such as high sensitivity, and stable charging properties, (3) wide selections of materials for use, (4) easiness of the production, (5) low cost, and (6) nontoxic.
Moreover, diameters of photoconductors have been recently reduced for downsizing image forming apparatuses, and high durability of photoconductors has been strongly desired because of the trends for high-speed of devices, and maintenance free. From this point of view, organic photoconductors have drawbacks that it is generally soft as a charge-transporting layer contains a low molecular charge-transporting material and an inert polymer as main components, and it is easily abraded by mechanical loads from a developing system or cleaning system after repetitive use in an electrophotographic process.
In addition, diameters of toner particles have been reduced to respond to the demands for high image quality. To improve cleaning ability accompanied with the toner of the reduced particle diameter, rubber hardness of a cleaning blade and contact pressure need to be increased for improving cleaning ability. This is another factor for accelerating abrasion of a photoconductor. Such abrasion of the photoconductor lowers the electric properties, such as deterioration of the sensitivity, and lowering the charging ability, which is a cause of image defects such as low image density and background depositions.
Moreover, the scratch formed by being locally abraded forms line-shaped smears in an image due to cleaning failures.
Accordingly, various attempts have been mend to improve abrasion resistance of organic photoconductors. Examples thereof include: a technology using a curable binder in a charge-transporting layer (see PTL 1); a technology using a high molecular charge-transporting material (see PTL 2); a technology where inorganic filler is dispersed in a charge-transporting layer (see PTL 3); a technology where a cured product of polyfunctional acrylate monomers is contained (see PTL 4); a technology of providing a charge-transporting layer formed with a coating liquid containing a monomer having carbon double bonds, a charge-transporting material having carbon double bonds, and a binder resin (see PTL 5); a technology where a compound obtained by curing a hole-transporting compound having two or more chain-polymerizable functional groups per molecule is contained (see PTL 6); a technology using a colloidal silica-contained cured silicone resin (see PTL 7); a technology of providing a resin layer formed by binding an organic silicon-modified hole-transporting compound into a curable organic silicon-based polymer (see PTLs 8 and 9); a technology where a curing siloxane resin having a charge-transporting properties donating group are cured in the three-dimensional network structure (see PTL 10); a technology where a resin that is three-dimensionally crosslinked with a charge-transporting material having at least one hydroxyl group, and conductive particles are contained (see PTL 11); a technology where a crosslinked resin formed by crosslinking a reactive charge-transporting material with polyol containing at least two hydroxyl groups, and an aromatic isocyanate compound is contained (see PTL 12); a technology where a melamine formaldehyde resin three-dimensionally crosslinked with a charge-transporting material having at least one hydroxyl group is contained (see PTL 13); and a technology where a resol-type phenol resin three-dimensionally crosslinked with a charge-transporting material having a hydroxyl group is contained (see PTL 14).